Area Forecast Discussion
Issued by NWS Blacksburg, VA

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406 FXUS61 KRNK 171740 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 140 PM EDT SUN MAY 17 2015 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL MAINTAIN A MOIST SOUTHERLY FLOW OF AIR ACROSS THE REGION THROUGH MONDAY. A COLD FRONT WILL SLOWLY APPROACH FROM THE WEST LATE MONDAY...MOVING THROUGH THE REGION TUESDAY. COOLER...DRIER AIR WILL FILTER INTO THE REGION BY THE MID PART OF NEXT WEEK BEHIND THE FRONT. && .NEAR TERM /THROUGH TONIGHT/...
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AT 1230 PM EDT SUNDAY... MADE SOME MINOR ADJUSTMENTS IN TEMPERATURES...CLOUD COVER AND POPS FOR THIS AFTERNOON. AT 1020 AM EDT SUNDAY... HIGH PRESSURE REMAINS OFF THE SOUTHEAST COAST WITH A WARM MOIST SOUTHERLY FLOW INTO OUR REGION WHICH CONTINUES INTO TONIGHT. THE UPPER LEVEL RIDGE REMAINS ANCHORED FROM FLORIDA THROUGH THE GREAT LAKE INTO MONDAY. A WEAK UPPER LEVEL DISTURBANCE KICKING OFF SCATTERED SHOWERS THIS MORNING AS IT ROTATES AROUND THE UPPER RIDGE. THE COMBINATION OF UPPER DISTURBANCES AND DAYTIME HEATING WILL RESULT IN THE DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS TODAY. UNDER THE UPPER LEVEL RIDGE...THE THREAT FOR MORE THAN ISOLATED PULSE SEVERE THUNDERSTORMS REMAINS LOW. THE MAIN CONCERN FOR THIS AFTERNOON INTO TONIGHT WILL THREAT FOR AREAS OF HEAVY RAIN AND LOCALIZED FLASH FLOODING DUE MAINLY TO A MOIST ATMOSPHERE...PRECIPITABLE WATER VALUES IN THE 1.5 TO 1.7 RANGE...AND LIGHT WIND SPEEDS MAKING FOR SLOW CELL MOVEMENT. ANY ANCHORING OR TRAINING OF CONVECTION MAY HELP THE POTENTIAL FOR WATER PROBLEMS. FOR THIS MORNING UPDATE...MODIFIED CLOUD COVER STARTING WITH SATELLITE IMAGE AND ITS TRENDS...THEN LEANED VALUES TOWARDS A BLEND OF THE CANREG AND GFS FROM LATE MORNING INTO THIS AFTERNOON. ADJUSTED POPS WITH CURRENT WSR-88D TRENDS AND BLENDED TOWARDS NAM FOR THIS MORNING WHICH CAPTURE BEST ONGOING CONVECTION. ADJUSTED TEMPERATURES WITH LATEST SFC OBS AND TRENDS...THEN COOL FORECASTED MID TO LATE MORNING RISING OF TEMPERATURES IN THE ISC TEMPERATURE GRIDS WITH THE RICH CLOUD COVER IN PLACE. STILL BELIEVE...HIGH TEMPERATURES THIS AFTERNOON COULD BE SIMILAR TO THOSE EXPERIENCE SATURDAY...RANGING FROM THE UPPER 70S ACROSS THE MOUNTAINS...TO THE MID 80S ACROSS THE PIEDMONT. OF COURSE...TEMPERATURES WILL DEPEND OF THE LIFTING OR MIXING OUT OF THE LOW CLOUDS AND FOG AND TIMING OF CONVECTION. WILL MONITOR ISC GRIDS FOR ADDITIONAL CHANGES. HAVE A GOOD SUNDAY! AS OF 400 AM EDT SUNDAY... LITTLE CHANGE IN THE UPPER LEVEL WEATHER PATTERN IS EXPECTED FOR TODAY AND TONIGHT...AS AN UPPER LEVEL RIDGE REMAINS SITUATED FROM FLORIDA THROUGH THE GREAT LAKES...WHILE SOUTHWESTERLY WIND FLOW IN THE LOW LEVELS OF THE ATMOSPHERE DRAWS WARM MOIST AIR NORTHWARD ALONG THE APPALACHIAN CHAIN. WILL START THE DAY WITH AREAS OF FOG BURNING OFF RAPIDLY AFTER 9 AM AS DAYTIME HEATING INCREASES...MAKING FOR A MIXTURE OF CLOUDS AND SUNSHINE...AS WELL AS A MUGGY FEEL TO THE AIR THROUGH THE REMAINDER OF THE MORNING. SHOWER AND THUNDERSTORM ACTIVITY WILL ONCE AGAIN BE DRIVEN BY DAYTIME HEATING...BEGINNING PRIMARILY OVER THE MOUNTAINS. EXPECT THE FIRST SHOWERS TO DEVELOP AROUND NOON NEAR THE BLUE RIDGE...WITH THE FIRST THUNDERSTORMS DEVELOPING SHORTLY THEREAFTER. SHOWER AND THUNDERSTORM ACTIVITY WILL SPREAD IN COVERAGE THROUGH THE AFTERNOON...WITH WESTERLY WINDS ALOFT CARRYING SOME OF THIS ACTIVITY ACROSS THE PIEDMONT DURING LATE AFTERNOON AND THE EVENING. RAINFALL COVERAGE AND INTENSITY WILL GRADUALLY FADE DURING THE EVENING WITH THE LOSS OF DAYTIME HEATING. CANNOT RULE OUT A FEW STRONG STORMS TODAY...BUT UNDER THE UPPER LEVEL RIDGE...THE THREAT FOR MORE THAN ISOLATED SEVERE THUNDERSTORMS REMAINS LOW. OF GREATER CONCERN WILL BE THE RENEWED THREAT FOR AREAS OF HEAVY RAIN AND LOCALIZED FLASH FLOODING DUE MAINLY TO A MOIST ATMOSPHERE...PRECIPITABLE WATER VALUES IN THE 1.5 TO 1.7 RANGE...AND LIGHT WIND SPEEDS MAKING FOR SLOW CELL MOVEMENT. HIGH TEMPERATURES THIS AFTERNOON WILL BE SIMILAR TO THOSE EXPERIENCE SATURDAY...RANGING FROM THE UPPER 70S AND LOW 80S ACROSS THE MOUNTAINS...TO THE MID 80S ACROSS THE PIEDMONT. AREAS OF CLOUD COVER AND CONTINUED SOUTHWESTERLY WINDFLOW AHEAD OF AN APPROACHING COLD FRONT WILL KEEP SUNDAY NIGHT LOWS IN THE LOW TO MID 60S AREAWIDE.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 400 AM EDT SUNDAY... UPPER RIDGE ANCHORED ACROSS THE MID-ATLANTIC REGION AND SOUTHEAST U.S. BEGINS TO BREAK DOWN AS UPPER LOW SHIFTS FROM THE NORTH CENTRAL PLAINS INTO THE GREAT LAKES. FRONTAL BOUNDARY...CURRENTLY ACROSS THE MIDWEST...SHIFTS INTO WV/KY/TN BY MONDAY EVENING. EXPECT GREATER INSOLATION IN ADVANCE OF THESE FEATURES THROUGH THE LATE MORNING/EARLY AFTERNOON MONDAY RESULTING IN A MORE UNSTABLE ENVIRONMENT AND THUS GREATER POTENTIAL FOR STRONGER THUNDERSTORMS THAN EXPECTED ON SUNDAY. IN ADDITION...WITH THE RIDGE BREAKING DOWN SOMEWHAT AND SHIFTING EAST TOWARD THE COAST...WOULD EXPECT A GREATER PERCENTAGE OF THE CONVECTION TO SPREAD INTO THE PIEDMONT THAN WE HAVE SEEN THE PAST FEW DAYS. THESE CONDITIONS ARE REFLECTED VIA THE CONVECTIVE PARAMETERS WITH CAPES IN THE 1000-2000 J/KG RANGE NEAR THE BLUE RIDGE BY AFTERNOON...LIFTED INDICES -3 TO -4. THE SIGNIFICANT SEVERE PARAMETER NEARS 20000 ACROSS THESE SAME AREAS BY AFTERNOON AS WELL. SPC CURRENTLY DOES NOT HAVE THE AREA OUTLOOKED...BUT WOULD NOT BE THE LEAST BIT SURPRISED TO SEE AT LEAST A MARGINAL ACROSS MUCH OF THE CWA WITH LATER OUTLOOKS. TEMPERATURES WILL BE WELL ABOVE NORMAL MONDAY...MOSTLY 70S MOUNTAINS TO NEAR 90 ACROSS THE PIEDMONT. GFS IS THE WARMEST...SHOWING LOW 90S AROUND DANVILLE. FOR TUESDAY...MODELS CONTINUE TO SLOW DOWN MOVING THE FRONT THROUGH THE REGION AS THE UPPER FLOW BECOMES INCREASINGLY ZONAL AND THE SUBTROPICAL RIDGE REMAINS ACROSS THE SOUTHEAST STATES. THE FRONT WILL LIKELY STALL ACROSS SOUTHERN NC OR NORTHERN SC INTO GA BY WED. THIS WILL LEAVE ENOUGH INSTABILITY/MOISTURE ACROSS THE REGION FOR SHOWERS AND A FEW THUNDERSTORMS TUESDAY MORNING ACROSS THE CWA...SHIFTING EAST OF THE BLUE RIDGE BY AFTERNOON. SPC HAS OUTLOOKED PARTS OF THE NORTHERN PIEDMONT/NORTHERN-CENTRAL VA FOR A MARGINAL RISK OF SEVERE TUESDAY...AND THIS LOOKS REASONABLE AND MAY WELL BE EXTENDED SOUTHWARD INTO OUR VA/NC PIEDMONT COUNTIES WITH LATER OUTLOOKS GIVEN THE PROGGED INSTABILITY. TEMPERATURES WILL STILL BE WELL ABOVE NORMAL IN THE EAST TUESDAY...BUT DROP BACK CLOSER TO NORMAL READINGS IN THE WEST. FOR WEDNESDAY...THE FRONT...AS NOTED ABOVE...SHOULD DRIFT SOUTH TOWARD THE NC/SC BORDER INTO THE MID-SOUTH STATES...BUT ALREADY BEGIN TO RETURN NORTHWARD INTO MIDDLE TN AS A WARM FRONT GIVEN THE ZONAL FLOW. LOW PRESSURE ACROSS THE NORTHEAST STATES SHOULD ALLOW COOL/DRY HIGH PRESSURE TO FILTER INTO OUR REGION FOR A COUPLE OF DAYS DROPPING DEWPOINTS INTO THE 40S/50S AND HIGH TEMPS INTO THE 60S/70S WEST TO LOWER 80S EAST...AND LOWS IN THE 40S AND 50S AS THE 0C 850MB ISOTHERM DIPS SOUTHWARD TO NEAR THE PA/WV BORDER WED. IT SHOULD BE A SIMILAR EVENT TO WHAT WE SAW WED OF LAST WEEK. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 430 AM EDT SUNDAY... AN OVERALL SPLIT FLOW PATTERN REMAINS IN PLACE AT THE BEGINNING OF THIS PERIOD WITH A DEEP UPPER LOW ACROSS THE NORTHEAST U.S. AND ANOTHER UPPER LOW ANCHORED ACROSS SOUTHERN CA...WITH A BROAD UPPER RIDGE ANCHORED IN BETWEEN THESE TWO LOW PRESSURE AREAS. A WEAK SHORT WAVE IS EVIDENT ACROSS THE CENTRAL PLAINS...EMANATING FROM THE SOUTHWEST U.S. UPPER LOW AND SPILLING OVER THE RIDGE. A WARM FRONT WILL BE EVIDENT ACROSS THE SOUTHEAST STATES INTO THE WESTERN TN VALLEY...THE LEFTOVER MID-WEEK FRONT STALLED TO OUR SOUTH. THE COMBINATION OF THE AFOREMENTIONED SHORT WAVE...THE RETURNING WARM FRONT...AND ANOTHER SHORT WAVE EVIDENT ROTATING AROUND THE BACK SIDE OF THE NORTHEAST U.S. UPPER LOW LEAVE QUESTIONS NOW AS TO WHETHER OR NOT THURSDAY WILL BE DRY AS EARLIER THOUGHT. CONFIDENCE HAS DECREASED IN THIS THINKING SUCH THAT LOW POPS HAVE BEEN INTRODUCED ACROSS MUCH OF THE CWA THU. THE NORTHERN STREAM SHORT WAVE SHOULD PUSH ANOTHER AREA OF HIGH PRESSURE INTO THE REGION BY SATURDAY AND SQUASH THE CHANCE OF PRECIPITATION AND MORE HUMID AIR BACK INTO THE SOUTHEAST STATES. THIS WILL HOLD UNTIL THE NEXT IMPULSE EJECTS FROM THE SOUTHWEST U.S. UPPER LOW REACHES THE REGION LATE IN THE WEEKEND...WHEN A RETURN TO CONDITIONS SIMILAR TO THOSE CURRENTLY IN PLACE APPEARS EVIDENT. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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AS OF 140 PM EDT SUNDAY... A COUPLE OF WEAK SHORTWAVES TRACKING ALONG THE WESTERN PERIPHERY OF THE UPPER RIDGE COMBINE WITH A VERY MOIST...INCREASINGLY UNSTABLE ATMOSPHERE ACROSS THE REGION WILL RESULT IN AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS...ESPECIALLY WEST OF THE BLUE RIDGE MOUNTAINS...WITH BRIEF PERIODS OF MVFR CIGS AND IFR VSBYS ALONG WITH GUSTY WINDS...MAINLY IN THE 18Z-02Z TIME FRAME. AFTERWARDS...THIS SHOULD SETTLE BACK TO MAINLY MVFR CIGS WEST/VFR CIGS EAST AND -SHRA/VCSH WEST OF THE BLUE RIDGE. AFT 06Z...FOG WILL LIKELY BECOME A PROBLEM ONCE AGAIN...WITH VISIBILITIES LOCALLY DROPPING INTO THE IFR-LIFR RANGE IN BR/FG. FOR WINDS...LIGHT SOUTHWEST 5-7KTS CONTINUE IN MOST LOCATIONS THIS AFTERNOON INTO TONIGHT...EXCEPT VARIABLE AND GUSTY IN/NEAR THUNDERSTORMS. WINDS OVERNIGHT WILL BECOME LIGHT AND VARIABLE OUTSIDE OF ANY SHOWERS. LATE NIGHT/EARLY MORNING FOG AND ASSOCIATED IFR-LIFR VSBYS/CIGS ARE HIGHLY LIKELY TONIGHT INTO MONDAY GIVEN THE SOUPY ATMOSPHERE IN PLACE. ONCE AGAIN SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED MONDAY AHEAD OF THE COLD FRONT. WESTERLY WINDS EXPECTED MONDAY AT 5 TO 10 KTS...LOCALLY HIGHER NEAR CONVECTION. MEDIUM TO HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WIND DURING THE TAF PERIOD. EXTENDED AVIATION DISCUSSION... LATE MONDAY INTO TUESDAY...A COLD FRONT MOVES THROUGH. THUNDERSTORMS SHOULD BE MOST NUMEROUS IN COVERAGE AND STRONGEST IN INTENSITY DURING THIS TIME FRAME FOR ALL AREAS...ENDING FROM THE WEST DURING TUESDAY. LONGER PERIODS OF MVFR CIGS/VSBYS APPEAR LIKELY MONDAY-TUESDAY. BEHIND THE COLD FRONT...DRIER/COOLER CONDITIONS ARE EXPECTED WED-THU WITH MOSTLY VFR CONDITIONS AS HIGH PRESSURE SLIDES IN FROM THE NW.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...KK/NF SHORT TERM...RAB LONG TERM...RAB/WERT AVIATION...KK/RAB

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